With respect to degradation of used polymers (or plastics), typically present as a product or material, it is noted that in general this is hindered by lack of separation methods (e.g. separation of a first polymer from a second polymer, such as polyethylene (PE) and polypropylene (PP)). As a consequence a significant amount of used polymers is used as a fuel, which is burned.
It is noted that chemical recycling of polymers such as Polyethylene terephthalate (PET) is considered cost-efficient only applying relatively high capacity recycling lines of e.g. more than 50 ktons/year. Most likely such lines will only be combined with production sites of very large polymer producers. Several attempts of industrial magnitude to establish such chemical recycling plants have been made in the past but without resounding success. Even the promising chemical recycling in e.g. Japan has not become an industrial break through so far; there seem to be two main reasons therefore: first, a difficulty of consistent and continuous waste bottles sourcing in a required huge amount at one single site, and, at second, the steadily increased prices and price volatility of collected bottles. So despite huge amounts of PET produced on a yearly basis (>50.000 ktons) forming similar amounts of waste no economically feasible process has been introduced.
A further issue is that if a separation is (partly) successful, degradation into smaller building units still is difficult. Many methods or processes are not selective enough, that is a discrimination, shown by a reagent in competitive attack on two or more substrates or on two or more positions in the same substrate, is relatively low. It is typically quantitatively expressed by ratios of rate constants of the competing reactions, or by the decadic logarithms of such ratios. Further a conversion is too low; efficient conversion of reactants (polymers) to desired products (monomers or oligomers) without much wastage production in terms of side products is an issue. As a consequence a yield, being regarded as a product of selectivity times conversion, is too low as well.
A problem with a use of catalysts, especially free catalysts in a solvent, is that it is virtually impossible to recover the catalyst after a first usage. As catalysts are typically quite expensive, one would like to recover a catalyst, at least largely, and reuse the catalyst a second time and preferably many more times. A small waste of catalyst would be acceptable, if a waste is in the order of a few percent or less. In this respect Wang (in Wang et al, “Fe-containing magnetic ionic liquid as an effective catalyst for glycolysis of poly(ethylene terephthalate)”, Cat. Comm. 11 (2010), pp. 763-767, and in Eur. Pol. J., Pergamon Press Oxford, vol. 45, no. 5, 1 May 2009, pp. 1535-1544), and Xueyuan Zhou et al. (in Pure and Applied Chemistry, Vol. 84, No. 3, 1 Jan. 2012, pp. 789-801) mention degradation of PET using a catalyst, without reusing the catalyst and with moderate results. The amount of catalyst used in these processes is relatively high (17-80 wt. %. catalyst per weight PET) and results are far from optimal.
Further it is in general considered a disadvantage to combine a catalyst to a support. Amongst others selectivity and conversion, as well as available catalyst are jeopardized. As such compared to non-combined catalyst typically more catalyst needs to be used in order to obtain similar results, and even then selectivity and conversion are still worse. In this respect Valkenberg et al. in “Immobilisation of ionic liquids on solid supports”, Green Chemistry, 2002 (4), pp. 88-93, shows ionic liquids attached to solid supports, e.g. a metal oxide, such as TiO2, SiO2, Al2O3, etc. Lee in “Functionalized imidazolium salts for task-specific ionic liquids and their applications”, Chem. Commun., 2006, pp. 1049-1063 mentions similar catalysts. Such relate to a two-phase system. The results of the catalytic activity tested are considered rather poor, apart from some exceptions, especially in terms of conversion and selectivity. Valkenberg, in table 3 shows a comparison between an Fe-IL in unsupported status and in supported status. For anisole the conversion drops from 90% to 6.5% (or about 30% for charcoal) and for m-xylene it drops from about 34% to 15% (or about 18% on charcoal). So a macroscopic support would typically not be considered for an ionic liquid in view of conversion. It is found important to further optimize reaction conditions. In other words the catalysts on a support would not be considered to be used.
In general most catalysts are used for synthesis of molecules and the like, not for degradation. Typically catalysts, and especially catalyst complexes, and function of a catalyst are sensitive to contaminants being present; in other words they function only properly under relative pure and clean conditions. As a result of contamination catalysts need to be replaced regularly, and extreme care is typically taken not to introduce contaminants. That may also be a reason why catalyst are typically not considered for degradation processes, as these processes almost inherently introduce contaminants.
In some instances metal catalysts are directly attached to a nanoparticle. Such catalysts are typically used for synthesis, but not for degradation, and certainly not for a reaction with at least one solid reactant. In this respect it is noted that for synthesis a reaction between two or more components is executed, wherein the two or more components are in close contact, such as in a solvent. The nature and relevant parameters of a synthesis reaction is considered to be quite different from degradation reactions; for instance relative low amounts of catalyst may be used and relatively high yield may be obtainable under optimal conditions. One can therefore not expect the teachings of synthesis reactions to be applicable in general to degradation reactions.
Reactions can take place in various types of reactors. In flow chemistry, a chemical reaction is run in a continuously flowing stream rather than in batch production. In other words, pumps move fluid into a tube, and where tubes join one another, the fluids contact one another. If these fluids are reactive, a reaction takes place. Flow chemistry is a well-established technique for use at a large scale when manufacturing large quantities of a given material. Often, microreactors are used.
Various patent documents and scientific documents recite fluids comprising magnetic particles.
Magnetic Fluids are a class of smart materials that change their properties reversibly and relatively fast (milliseconds) under presence of an external magnetic field. These fluids can show changes in apparent viscosity of several orders of magnitude when a magnetic field is applied, such as a magnetic flux density in the order of around 1 T.
The present invention provides an improved method for degrading polymers typically present in a polymer material which overcomes at least one of the above disadvantages, without jeopardizing functionality and advantages.